Chapter 12 Sulfur and Chapter 13 carbonates

Question 1

What are the uses of sulfur (2)

Answer 1

Gunpowder

manufacture of sulfric acid

Question 2

How is sulfric acid manufactured? explain using the contact process.

Answer 2

1. Sulfur is burned in the presence of oxygen to produce sulfur dioixide
   S + O2 —-> SO2
2. Sulfur dioxideis mixed with ecess air and passed over a vanadium (v) oxide catalyst forming sulfur trioxide
   2SO 2 (g) + O 2 (g) ⇌ 2SO 3 (g)
3. Sulfuric trioxide is dissolved in concetrated sulfric acid to form oleum (a thick fuming liquid)
   H2SO4 + SO3 —-> H2S2O7
4. Water is added to oleuim to make concetrated sulfric acid
   H2S2O7 + H2O —-> 2H2SO4

Question 3

What are the conditions for the second step of the contact process

Answer 3

High temperature - Catalysts pellets heated to 450 degrees
Excess of air - ensures all SO2 converts to SO3
Exothermic - Lower temperature = greater yield but not economically viable
Lower pressure - around 2 atm

Question 4

What is the chemical formula for lime

Answer 4

CaO Calcium oxide

Question 5

How is lime produced using limestone

Answer 5

Calcium carbonate (limestone) + (heat) —-> Calcium oxide (lime) + Carbon dioxide

CaCO3 —-> CaO + CO2

Question 6

Define thermal decomposition

Answer 6

When one reactant is heated and two or more products are formed

Question 7

How is slaked lime formed

Answer 7

Calcium oxide + water —> Calcium hydroxide

CaO (lime) + H2O ——> Ca(OH)2 ( slaked lime)

Question 8

Uses of limestone, lime, and slaked lime (2)

Answer 8

treating acidic soil neutralising

acidic industrial waste products